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// Copyright © 2021 siddharth <s@ricketyspace.net>
// SPDX-License-Identifier: ISC
package lib
// Average Word Length (English).
const awl float64 = 4.7
// 'hs' must be a hex encoded string.
func XORCrackSingleKey(hs string) (byte, string, float64) {
l := len(hs) / 2
var k byte = 0
var ds string = ""
var scr float64 = 100.0
i := byte(0)
as := []byte(HexStrToAsciiStr(hs))
for i < 255 {
ks := FillBytes(i, l)
xs := FixedXORBytes(as, ks)
s := phraseScore(string(xs))
if s < scr {
k = i
ds = string(xs)
scr = s
}
i += 1
}
return k, ds, scr
}
func phraseScore(phrase string) float64 {
pl := len(phrase)
// Expected number of words.
ew := float64(pl) / awl
// Number of words in phrase.
ws := 0.0
for i := 0; i < pl; i++ {
if phrase[i] == ' ' {
ws += 1.0
}
}
ws += 1.0
// Compute score.
score := 1.0 - (ws / ew)
if score < 0 {
score *= -1
}
return score
}
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